This invention relates to a refining roll drive for chocolate refining machines.
As is known, with chocolate refining machines, the individual rolls are supported in succession and held in mutual operative connection through their rotary drive gearing. The gears are spiral gears. Accordingly, the drive ratio is a fixed one. Refining machines, as well as pre-refining machines, normally include five rolls, of which the first two form the feeding roll pair, while the third, fourth and fifth rolls form the refining rolls proper. Actually a rectifying action is also performed, however, by the second or feeding roll, which cooperates with the third refining roll. In order to achieve a thickness of the chocolate film being delivered which is as even as possible, the rolls of prior refining machines have a crowned design. Such rolls are then ground when worn. At the same time, their gears are also ground. This grinding operation may usually be carried out once or twice, and is a time-consuming and costly one because it can only be performed, as a rule, at the manufacturer's facilities, which may sometimes be located in some other country, and even in different continents.
In recent years, the Assignee herein disclosed a chocolate refining machine (Italian Patent Application No. 21 857/83) corresponding to U.S. patent application Ser. No. 585,297, filed Mar. 1, 1984, now U.S. Pat. No. 4,603,815, wherein the rolls are manufactured without a crown, a crown-equivalent effect being obtained by letting the rolls rock in a horizontal plane relatively to one another. However, the roll rocking or oscillatory movements are of very low magnitudes, e.g. of about 1 to 2 degrees. The roll oscillations are produced by means of oscillating supports which cooperate with displacement actuators associated therewith.
With conventional refining machines, moreover, the roll rotary drive gears are supported on one side member defining a lubrication chamber having an ample supply of lubricant oil stored in its bottom portion and an oil delivery pump.
The drives equipping prior refining machines have several deficiencies and disadvantages, the outstanding ones of which are listed here below:
the refining roll grinding also involves grinding of the drive gears, which is an expensive procedure and results in the original drive ratios of the machine being altered. Such grinding, which becomes necessary after a number of hours of operation, can only be performed once or twice, for otherwise, dimensional changes would be so significant as to require replacement of the gears or rolls. Consequently, the life of known rectifying machines cannot be extended beyond a certain limit.
The mutual mesh engagement of the refining roll gears results in considerable inflexibility of the drive ratios, whereas to effect the plasticity of the chocolate to be treated, an ability to change them within limits would be desirable.
That end of the refining machine which houses the refining roll gears is constructed as a lubricating chamber containing oil for continuous lubrication and a delivery pump. This chamber requires to be sealed and is closed by means of a large number of bolts. Access to the gears involves preliminary emptying of the oil chamber and removal of the bolts. The time required is quite considerable.
The presence of lubricating oil is increasingly more objected to by food article hygiene regulatory bodies to prevent the assumption of any oil, or smell thereof, into the products being processed.
The drive power is transmitted to one end of a refining roll, generally the delivery roll, so that the torque input end support of the same is applied very high forces tending, as is known, to bend it arcuately. This seriously affects the uniformity of the delivery nip and results in uneven thickness of the chocolate film being delivered. Furthermore, the driving power must be quite high because its transmission by means of V-belts would involve high frictional resistances between the pulleys and belts.
The high powers involved and their direct transmission through gears result in vibration, and by reflection, in noisy operation.
For such drive types spiral gears are employed. These create significant axial stresses on the roll bearings, which bearings are subjected to the adverse effect of a composite, axial and radial, stress.
With single drive refining machines, or machines having separate drives for each roll, it has been found that such a fractioned drive system is in practice even too sophisticated relatively to the interventions required to effect appropriate speed changes to affect the plasticity or degree of fineness of the chocolate being processed.